Damper for furnaces



Dec. 5, 1933. T. H. BANFIELD DAMPER FOR'FURNACES Filed July 25, 1928 2 Sheets-Sheet l 1933- T. H. BANFIELD 'DAMPER FOR FURNACES Filed July 25, 1928 2 Sheets-Sheet 2 Patented Dec. 5, 1933 UNITED- STATES PIOXTENT OFFICE.

7 6 Claims.

This invention relates generally to coal burning furnaces and particularly to means for regulating the supply of air delivered to the combustion of such furnaces.

The main object of this invention is to provide an exceedingly simple and eificient form of damper by means of which the orifice can be easily and accurately varied.

The second object is to provide a damper which will eliminate the tendency of blowing back on the part of the fan as is common when certain types of dampers are employed.

The third object is to so construct the damper n that the opening may be varied from the maximum to the minimum diameterlby a lever movement, which lever is capable of being held in various semi-fixed positions.

The fourth object is to so construct the damper that a shaft may be passed through the center 29 thereof without interfering with its operation.

These, and other objects, will become more apparent from the specification following as illustrated in the accompanying drawings, in

- which:

Figure l is a perspective view showing a typical form of Stoker to which this device is attached. Figure 2 is a large front elevation of the damper with parts broken away. Figure 3 is a fragmentary section taken along the line 30 33 in Figure 2. Figure 4 is a detail of the operating ring. Figure 5 is. a detail of one blade. Figure 6 is an edge elevation of the blade shown in Figure 5. Figure 7 is a diagrammatic rear view showing one blade in place and showing in dotted lines the position of the same blade for maximum opening. Figure 8 is asection taken along the line 88 in Figure 7. Figure 9 is a section taken along the line 99 in Figure '7.

Similar numbers of reference refer to similar parts throughout the several views.

Referring in detail to the drawings, there is illustrated the front of a furnace 10 in which is placeda tuyere box 11 to which coal is fed from the hopper 12 through a fuel duct 13 and to which air is fed through an air duct 14 by a fan 15. The speed of the fan on such devices is practically constant and the flow of air through the duct 14 is controlled by restriction. This is ordinarily done by means of a winged damper, but in this instance there is employed an iris damper which consists of a damper frame 16 having a somewhat sloping outer face 17 over which is secured a screen 18 by means of the ring 19 and the screws 20. The damper frame 16 is secured to the fan casing 15 by means of the bolts 21. On the rear or inner side of the damper frame 16 is placed an operating ring 22 provided with holes 23 around its central opening 24. The ring 22 is provided with an operating handle 25 on the rear side of which is placed a spring-urged pall 26 adapted to engage the notches 2'7 to the outer rim'of the damper frame 16.

The blades 28 of the iris damper are Somewhat curved and widened at the end 29 which is providecl with a pivot 30 formed from the material in the blade 28 itself. The end 31 is relatively straight and narrow and is provided with a pivot 32, also formed from the material in the blade 28, but on the opposite side of the pivot 30. The pivot 30 on the wide end 29 of each blade 28 is placed in a hole 23, the blades overlapping each other in successive order allowing the pivot 32 of each blade to project rearwardly or toward the fan and well toward the outside of the damper. The cover plate 33 provided with the slotted openings 34 is now placed over the blades, each pivot 32 being held and guided by a respective slot 34. In order to prevent the relatively thin blades 28 from being bent by inrushing air, reinforcing bars 35 are provided, whose bent ends 36 are held by the prongs 37 which are pushed out of the metal in the ring 33 and afterwards bent down upon the bars 35, as shown in Figure 9. The damper frame 16 is provided with a slot 38 whose ends 39 form stops for thelever 25 and limit its rotative movement.

The operation of the damper is as follows: When desiring to permit the maximum amount of air to pass into the fan, the lever 25 is moved toward the left as shown in Figure 2. To decrease this amount it is merely moved in the opposite direction. Provision is made for stopping the lever 25 by means of the pawl 26 to prevent any possibility of a change in the damper settings due, to vibrations, and also to assist one in-securing a certain damper opening whenever desired, namely, the lever can be set at the first, second, third, fourth or fifth notch, which will always give a definite size of 0 damper opening. While it is possible to practicallyclose .the opening entirely, if desired, by merely positioning the slot ends 39 to permit this action, this is not always desirable as in numerous instances a shaft is passed through the damper and by making the stop on the lever the blades can always be held out of contact with the shaft.

The blowing back on the part of the fan is entirely eliminated because the distance from the edge of the iris to the center can be controlled so as to make this radial distance less than the zone of pressure within the fan built up by the blades. With a rose or a shutter damper the radial distance from the center to the far edge of the opening is fixed and cannot be altered by partially closing the damper. Consequently whenever the pressure builds up from the periphery to such far point, the dust will be blown out at the far, point while, with the iris damper, the distance of the far point is altered and consequently there is no tendency to blow restricting the size of the intake opening while keeping the opening constantly concentric with the axis of the fan shaft.

2. The combination with an underfeed stoker of a centrifugal fan delivering combustion air to the fire, a casing for said fan having an axial intake opening, and an iris diafram for closing the intake opening of the fan casing.

3. In combination; a retort, tuyres surrounding the retort, an air duct delivering air to the tuyeres, a fan casing having a substantially circular intake opening and an exit communicating with the air duct, a tangential discharge fan within the fan casing and axially arranged with respect to the intake opening, and means for increasing or decreasing by small amounts the size of the intake opening while maintaining said substantially circular intake opening constantly concentric with the fan shaft.

4. The combination with an underfeed stoker of the type having a feed hopper, a fan, a fan casing surrounding the fan and having an intake opening to admit air axially to the fan, a retort, a fuel duct leading from the hopper to the retort, fuel feeding means for forcing fuel thru said duct from the hopper to the retort, a parallel duct for leading air from the fan to the retort, and a motor, for driving the fuel feeding means and the fan, of means for restricting at will the size of the substantially circular intake opening to the fan while maintaining the opening, irerspective of its diameter, constantly concentric with the shaft of the fan.

5. The device of claim 2 in which the last means is a manually operated iris diafram.

6. The device of claim 2 plus means between the fan and the blades of the iris diafram for supporting the blades against pressure from the outside of the diafram and toward the fan, said means engaging a plurality of the blades between their two ends.

THOMAS H. BANFIELD. 

